There are downsides. One is that the coffinlike confines spook claustrophobes, possibly distorting their reactions to stimuli. The other is that brain imaging is expensive. The moving-image MRI rents for $1,000 an hour at Emory University in Atlanta; a single experiment, which includes at least 12 subjects, can cost $50,000.

But much is at stake: $117 billion was spent last year on advertising in the U.S., not to mention $6.8 billion on, among other things, focus groups, opinion polling and ad and market tracking (says Inside Research newsletter), or the untold sums invested in 22,000 new consumer packaged goods per year.

As companies continue to learn about how our brains work, they will try to stimulate areas involved in preferences, purchasing decisions, even aspirations. Using MRI and other technology, DaimlerChrysler's research center in Ulm is studying the brains of drivers as they interact with cars. Some of that work is to design navigational and warning devices for a safer vehicle. Some is driven by the pure marketing goal of seeing how drivers' brains respond to specific images of autos. Daimler knows, for example, that when people look at the front of a sports car, a part of the brain that responds to faces--in the back of the brain where the cerebrum touches the cerebellum--comes alive. This may happen because the headlights are eyelike. Could the Mini Cooper be such a success partly because its "face" reminds some people of a friendly cartoon character?

You don't need a Ph.D. to put the more mundane aspects of psychomarketing to work. Market Connections International, a small firm in Montclair, N.J., pitches "environment-conditioned marketing" to such clients as Colgate-Palmolive, Kraft Foods and Unilever Group. It distributes product samples to vacationers to create a mental association between the product and having fun. "If you introduce a product to people on vacation when they are in a good mood, and they see that in a store later--bang!--that comes back to them the way the bell worked with Pavlov's dogs," says Bailey, the professor at George Washington.

Memory plays a critical role in product choice. In a recent shopping study conducted by the Open University in Milton Keynes, U.K. and the London Business School, scientists found that when shoppers are asked to make a choice among common and closely related items in a grocery-store-like setting, the areas of the brain involved in memory light up like a July 4th nighttime sky. When buyers choose a brand they really care about, neural activity suggests that they are making an emotional choice based on past experience, says Steven P.R. Rose, a professor of biology and director of brain and behavior research at the university. The study was funded by a supermarket and three other companies Rose won't name.

Companies of all types, among them Kellogg and Procter & Gamble, are more interested than ever in probing emotions. The cereal maker recently hired cognitive psychologist Angela Fratianne Weltman to explore women's conflicting feelings about food. Result: Instead of pitching Special K simply as a low-fat breakfast food, Kellogg is featuring average women caught between polar passions for doughnuts and great-looking legs. P&G has looked into the question of whether consumers harbor secret feelings for, of all things, toilet paper (see box, p. 70). Loopy or no, the assumptions are born out of brain research. Neurologist Antonio Damasio, a professor at the University of Iowa College of Medicine, suggests in his book Descartes' Error that emotion is critical to effective thinking and decision making. That may explain why offers like 99-cent hamburgers and 0% financing on cars--which appeal strictly to cold common sense--sometimes backfire.

It's not just our own emotions that play a part. Gregory S. Berns, a psychiatrist at Emory, is using brain imaging to demonstrate the effects of peer pressure on individual perception, with the idea of explaining the development of fads, from investment trends to the popularity of Burberry plaids and belly button rings. "There is probably some reward or kick in conforming to a group," says Berns, who believes most buying decisions are driven by the subconscious.

Berns recently put 30 subjects into MRI machines, where he asked them to compare 54 pairs of abstract three-dimensional images and decide if they were alike or different. Throughout the 75-minute test participants were shown responses given by four other subjects, while the MRI machine snapped 1,000 brain images.

This reporter lay down as a guinea pig. While in the scanner she was shown responses of four other subjects to the pairs of objects before seeing them herself, then performed the mental rotation required to evaluate the images. Lemminglike, she usually went along with the majority view, even when it was wrong. Her brain scan shows why: a change in perceptual processing. By measuring relative degrees of activation in the parietal lobe, an area involved in integrating visual images, and in the prefrontal cortex, where decision making takes place, Berns says, he could determine that the group changed what the reporter perceived.

This experiment is one of a series of studies in the growing field of neuroeconomics, which investigates how people calculate risks and rewards. It is being funded by James Richards, a wealthy Atlantan who says he wants to understand the role of investor emotions in the purchase and sale of securities. The research could ultimately show that the brains of repeatedly successful investors subconsciously detect patterns before others notice them.

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